Universal Serial Bus (USB)

Having replaced serial ports, parallel ports, PS/2 ports and other legacy connectors, USB has furthered its activities through incremental bandwidth upgrades, a robust common connector for all peripherals, and by its worldwide acceptance. There is, however, one significant shortcoming that casts a long shadow over the many advantages of USB: cable distance limitations. USB 1.1 and 2.0 have a cable limit of five metres and although USB 3.0 with its higher throughput, has no precise limit, the best range for consistent transmission is about three metres.


To address this five metre cable length limitation, Icron Technologies created ExtremeUSB®, thus enabling integrated USB connections to reach beyond the desktop. This patented protocol masters the stringent timing requirements of the USB specification enabling USB connections over all physical media, including Cat 5e cabling and fibre optics.

Features of ExtremeUSB

Icron Technologies have been developing ExtremeUSB since 1998, enabling embedded solutions for pro AV, industrial control, medical, security, and remote desktop applications. Icron has led the way in extension expertise, and ExtremeUSB is currently the unrivalled champion in the marketplace. Its benefits are unmistakeable:

  • It requires no new driver installation, being true plug and play.
  • It supports USB 2.0 (high‐speed) and USB 1.1 (full‐speed, low‐speed) devices.
  • It operates with USB 2.0 high speed host controllers and USB 1.1 classic hosts.
  • It supports all key operating systems including Windows®, MAC OS®, and Linux.

ExtremeUSB System Topology

Essentially, an ExtremeUSB link comprises a local extender (LEX), a remote extender (REX), a host computer, and USB device(s). The LEX is connected to the host computer and the REX to the USB devices. Between the LEX and the REX is the connection media, for example, Cat 5e (or better cabling).

Put simply, the LEX manages the expectations of the host computer and the REX manages the expectations of the USB devices. In both cases, ExtremeUSB keeps the link active during the increased delays resulting from the link extension.